Drum Instruction
Programming
6--13
Drum Instruction Programming
DL105 PLC User Manual, 3rd Edition
Drum instructions use four counters in the CPU. The ladder program can read the
counter values for the drum’s status. The ladder program may write a new preset
step number to CT(n+2) at any time. However, the other counters are for monitoring
purposes only.
Counter Number Ranges of (n) Function Counter Bit Function
CT(n) 0--74 Counts in step CTn = Drum Complete
C( n+1) 1--75 Timer value CT(n+1) = (not used)
CT( n+2) 2--76 Preset Step CT(n+2) = (not used)
CT( n+3) 3--77 Current Step CT(n+1) = (not used)
The following ladder program shows the EDRUM instruction in a typical ladder
program, as shown by DirectSOFT. Steps 1 through 11 are used, and all sixteen
output points are used. The preset step is step 1. The timebase runs at (K100 x 0.01)
= 0.1 second per count. Therefore, the duration of step 1 is (5 x 0.1) = 0.5 seconds.
Note that step 1 is time-based only (event = “K0000”). And, the output pattern for
step 1 programs all outputs off, which is a typically desirable powerup condition. In
the last rung, the Drum Complete bit (CT4) turns on output Y0 upon completion of the
last step (step 10). A drum reset also resets CT4.
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